The invention relates to a device for coating a substrate, preferably with aluminum oxide, using a direct current source and/or an alternating current source which is connected to an electrode disposed in an evacuable coating chamber. The electrode in turn is electrically connected to a target to be sputtered and the sputtered particles thereof are deposited on the substrate, for example, a plastic element. A process gas can be introduced into the coating chamber and toroidal magnetic fields penetrate the target and the flux lines exit from the surface of the target in the area of the magnetic poles.
A cathode sputtering device is known (German OS 27 07 144; Sloan Technology Corp.) including a cathode which has one surface to be sputtered, and a magnetic device at the side close to the cathode and at the side for generating magnetic flux lines opposite the surface to be sputtered. At least a few of these flux lines enter the surface to be sputtered to exit it again a intersections which are spaced apart and between which the flux lines form continuously archlike segments spaced from the surface to be sputtered. Together with the flux lines, the surface forms a boundary for a closed area thus forming a tunnel-like area which is located above a thus defined path on the surface to be sputtered. Charged particles show a tendency of being restrained in the tunnel-like area where they move along. The invention also includes an anode in the vicinity of the cathode and a connection of the cathode and the anode to a source of an electric potential whereby at least the surface to be sputtered is within an evacuable container.
This device includes a moving device for generating a relative movement between the magnetic field and the surface to be sputtered while maintaining the spatial relationship. The aforementioned defined path covers a surface area which is greater than the surface area occupied by the resting path.
Further, an arrangement is known for coating a substrate with a dielectric (P 38 21 207.2, Leybold AG) having a direct current source which is connected to an electrode which in turn is electrically connected to a target to be sputtered. The sputtered particles combine with a substance to be supplied so as to form a compound which is deposited on the substrate. Toroidal magnetic fields penetrate the target and the flux lines exit the surface of the target in the area of the magnetic pole. This arrangement is provided with an alternating current source the output voltage of which overrides direct voltage of the direct current source. The electric power of the alternating current source which is supplied to the electrode corresponds to 5% to 25% of the power supplied to the electrode from the direct current source.
Finally, a magnetron sputtering cathode for vacuum coating systems having a circular target plate made of the material to be sputtered was suggested (DE 36 19 194, to which U.S. Pat. No. 4,746,417 corresponds, Leybold AG) which includes at least one magnet system disposed behind the target plate. This magnet system includes two self-contained rows of permanent magnets nesting in one another and the magnets of each row have the sam pole position whereas the pole position of the magnets of the two rows is opposite with respect to one another such that above the target plate the magnetic field lines form at least one self-contained tunnel starting at the one row of magnets and returning to the other row of magnets. The invention further includes a driving device for continuously rotating the magnet system around the center axis of the target plate. A first magnet system for generating a first magnetic tunnel which is essentially concentric to the rotating axis is disposed at the edge of the target plate. An eccentrically offset second magnetic system is disposed between the rotating axis and the first magnet system. It generates a second magnetic tunnel covering only one sector of the target plate such that when both magnet systems perform one common rotation, the surface elements of the target plate are subject to the product of residence time and intensity in a way that in the center area the target plate is subject to a regular abrasion whereas the abrasion is stronger at the edge so that a substrate field opposite the target plate is uniformly coated.